Air conditioning apparatuses capable of providing so-called desiccant air conditioning have been known in the prior art. Such a desiccant air conditioning apparatus is so configured as to perform air conditioning by controlling the humidity level of air for supply to indoor spaces. The desiccant air conditioning apparatus has constructional equipment including an adsorption element, a heater, a cooler et cetera. The adsorption element performs moisture adsorption/desorption by passage of adsorption air or regeneration air. For example, Japanese Patent Kokai Publication No. (1997)318127 describes an air conditioning apparatus employing two adsorption elements of the above-described type. In this prior art air conditioning apparatus, either a dehumidified air stream or a humidified air stream is continuously supplied to an indoor space by switching between a first state in which moisture contained in adsorption air is adsorbed by one of the adsorption elements simultaneously with regeneration of the other adsorption element by regeneration air and a second state in which one of the adsorption elements is regenerated by regeneration air simultaneously with adsorption of moisture contained in adsorption air by the other adsorption element.
Apart from that, dehumidification of adsorption air by the adsorption element will give rise to generation of heat of adsorption. And, if the adsorption air temperature is raised, this lowers adsorption performance. To deal with this problem, a technical proposal of cooling the adsorption element by the use of cooling air has been made.
Such a type of adsorption element which is made cool by cooling air is provided with a humidity adjusting side passageway through which adsorption air or regeneration air flows and a cooling side passageway through which cooling air flows. And, the cooling side passageway is configured so that heat of adsorption, generated when adsorption air passes through the humidity adjusting side passageway, is absorbed by cooling air.
In the above-described air conditioning apparatus, adsorption air is forced to flow through the humidity adjusting side passageway of the adsorption element so that the adsorption air is dehumidified. Furthermore, the adsorption air thus dehumidified is cooled by a cooler for supply to an indoor space. In this way, a cooling mode of operation is performed. At this time, cooling air flows through the cooling side passageway of the adsorption element, whereby the adsorption air is cooled. Thereafter, the cooling air is discharged outdoors. In addition, when large amounts of moisture are adsorbed on the adsorption element after the operation is carried out for a predetermined period of time, regenerating air, heated to a high temperature by the heater, is forced to flow through the humidity adjusting side passageway. As a result, the adsorption element is regenerated.
In the conventional air conditioning apparatuses, outdoor air serves as cooling air. Because of this, cooling efficiency is low during hot climate conditions such as summer, thereby producing the problem that heat of adsorption in the humidity adjusting side passageway cannot be collected in satisfactory manner. And, in such a case, the adsorption performance of the apparatus finally falls.
Bearing in mind that the conventional air conditioning apparatuses suffer the above-described drawbacks, the present invention was made. Accordingly, an object of the present invention is to provide improved cooling efficiencies in the case where an adsorption element, the temperature of which is raised by heat of adsorption generated when adsorption air flows through a humidity adjusting side passageway, is cooled by the use of cooling air.